The present invention relates to mixing apparatus of the type used in laboratories. Such equipment, as a laboratory instrument, may have a wide range of uses, from general stirring applications to those with more exacting requirements such as aliquot mixings, extraction procedures and reagent preparation.
In stirring or mixing applications of this type, it is noted that the plate or tray on which the containers or holders are supported is not rotated in the true sense of the word--rather, the center of the plate, and all other points on the plate, are driven in small circles so that any given line on the plate remains parallel to the same line during the entire orbital motion. The orbit may be circular, or it may be elliptical. Orbiting stirring devices of this type are known in the art, and the following patents are representative of the state of the art: U.S. Pat. Nos. 681,254; 2,828,949; 2,976,792; 3,184,222; and 3,396,947.
According to the present invention, a platform or tray for holding laboratory containers such as test tubes or the like is driven in orbital motion by an eccentric drive mechanism housed in a cabinet. A first pair of parallel tracks of inverted channel shape, is secured to the bottom of the platform, and a second pair of parallel tracks, also of channel shape, is mounted to the top of the cabinet. The first and second pairs of tracks extend transverse of each other.
Between the two pairs of tracks is an intermediate plate having a large central aperture so that the drive shaft for the platform can rotate is located between the two pairs of tracks. Four disc-shaped bearing elements are mounted to the intermediate plate, extending to either side thereof, in the form of a square. Each bearing element is received in and coupled to an upper and a lower track to maintain the platform in the same disposition during its orbital motion.
The motor and drive train which actuates the platform are housed in the cabinet, and they are mounted with shockproof of vibration-free elements so as to minimize operating noise.
The system operates in either a continuous mode or a timed mode under control of a switch. In the timed mode, the operator determines the time of operation by setting a knob.
The main drive motor which actuates the platform also drives a small dc motor which acts as a tachometer. The terminal voltage of the tachometer motor is displayed as a signal representing the revolutions per minute of the platform. The speed of operation may also be set by the operator, by adjusting a knob which controls an electronic control system. The speed of operation is variable in a continuous linear manner within the design range.
A thin layer of sponge runner is provided on the upper surface of the platform to prevent laboratory ware from creeping off the platform during operation. The platform is provided with a raised outer rim so that slides may be placed on the platform and will not be thrown off at high speeds. Holes are provided in the rim for securing containers to the platform during high-speed operation.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.